Simple azimuth calibration without encoders ?

[skysurfer]

For looking up objects I use an electronic altimeter to set the altitude and an azimuth circle to set the azimuth. However, the latter must be calibrated every session. The altimeter is easy to calibrate once (with a bubble level) as the bubble level has a hard zero altitude value.

And the altimeter is accurate within 0.2 degrees, while a smartphone's inclinometer has an accuracy of only 2-3 degrees.

The azimuth can theoretically be achieved by a compass, but in all cases as far as I know the accuracy is not better than several degrees.

Is there a way to get the azimuth to an accuracy of less than 0.5 degree ?

[AndrewJ]

Gday Skysurfer

Just pick a known bright star and centre it.
Calc its expected azimuth for that time using a phone app like SkSafari etc
Set The Azimuth circle to match

Andrew

[kinetic]

Great suggestion, Andrew.
FWIW maybe if you intend to plonk the dob in the same spot in the backyard, then can I suggest putting in some reference pavers on
the ground or lawn you sit it on, fix a cheap laser pointer on the
dob base somewhere, do a calibration as Andrew states and
then mark a spot on a distant wall the laser points too.
That way, any other night you set up just pointing the laser at the same
mark on the wall will give you your azimuth reference point.

Or you could simply just do Andrew's calibration method every night.
Steve

[SteveInNZ]

If you're observing from the same place, find a prominent object that you can find in the dark and use Google Earth or the Photographer's Ephemeris or similar to find the azimuth from your location.
For me, the left side of the second power pylon is due north.

Steve.

[skysurfer]

This method I already use, but every observing session my scope is placed in a different location. The only guess I have is that the brick paved paths have an azimuth of 150 and 240 degrees.
As I need reading glasses (which do not work for objectes > 1 meter) to read off the coordinates from my phone's screen (which is dim red at night, no bright night vision killing full color) I have found a trick. I use now a screen magnifier (Android: triple click on the screen, under iOS three finger single click) which eliminates the need for reading glasses which works much more quickly.

The laser is a good idea. I'll try that.